Vibroseis, as known in the art, is a method used in exploration seismology to propagate energy signals into the earth over an extended period of time as opposed to the near instantaneous energy provided by an impulsive source such as explosives or weight-drop trucks. Data recorded in this way can be correlated to convert the extended source signal into an impulse. Generally, the signal has been generated by a servo-controlled hydraulic vibrator or shaker unit mounted on a mobile base unit.
Techniques for using seismic waves to probe for oil reserves or other geological structures and/or anomalies in the earth are becoming quite sophisticated. The key requisite for the work is a high fidelity ground shaker whose force, frequency, and phase can be controlled precisely. Currently, hydraulic shakers dominate the industry. These devices can be truck-mounted for mobility. Generally, with hydraulic shakers, small mechanical actuators control high pressure hydraulic fluid flow to apply sinusoidal compressive forces to a baseplate. Large forces can be achieved with this design. Yet, there are drawbacks to hydraulic shakers. The use of hydraulic fluids can impose environmental concerns regarding leaks and spillage. Furthermore, hydraulic shakers generally are relatively slow-responding, which can result in decreased fidelity to the input signal.